Datasheet

LM2578A, LM3578A
www.ti.com SNVS767E –AUGUST 2000–REVISED APRIL 2013
R1 = (|V
o
| +1) R2 where R2 = 10 kΩ.
R3 = V/(I
L(max, DC)
+ 0.5 ΔI
L
).
R4 = 10V
BE1
B
f
/(I
L (max, DC)
+ 0.5 ΔI
L
)
where:
V, V
BE1
, V
sat
, and B
f
are defined in the Buck Converter with Boosted Output Current section.
ΔI
L
= 2(I
LOAD(min)
)(V
in
+|V
o
|)/V
IN
R5 is defined in the Buck Converter with Boosted Output Current section.
R6 serves the same purpose as R4 in the Boost Regulator circuit and is typically 220 kΩ.
C1, C3 and C4 are defined in the Boost Regulator section.
C2 ≥ I
o
|V
o
|/[f
osc
(|V
o
| + V
in
) V
ripple
]
L1 is found as outlined in the section on buck converters, using the inductance chart of Figure 29 for the invert
configuration and 20% discontinuity.
V
in
= 5V R4 = 190Ω
V
o
= −15V R5 = 82Ω
V
ripple
= 5 mV R6 = 220 kΩ
I
o
= 300 mA C1 = 1820 pF
I
min
= 60 mA C2 = 1000 μF
f
osc
= 50 kHz C3 = 20 pF
R1 = 160 kΩ C4 = 0.0022 μF
R2 = 10 kΩ L1 = 150 μH
R3 = 0.01Ω D1 = 1N5818
Figure 34. Inverting Regulator
BUCK-BOOST REGULATOR
The Buck-Boost Regulator, shown in Figure 35, may step a voltage up or down, depending upon whether or not
the desired output voltage is greater or less than the input voltage. In this case, the output voltage is 12V with an
input voltage from 9V to 15V. The circuit exhibits an efficiency of 75%, with a load regulation of 60 mV (10 mA to
100 mA) and a line regulation of 52 mV.
R1 = (V
o
− 1) R2 where R2 = 10 kΩ
R3 = V/0. 75A
R4, C1, C3 and C4 are defined in the Boost Regulator section.
D1 and D2 are Schottky type diodes such as the 1N5818 or 1N5819.
Copyright © 2000–2013, Texas Instruments Incorporated Submit Documentation Feedback 19
Product Folder Links: LM2578A LM3578A